Browsing by Author "Ararsa, Bekele"

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    Capacity and Passenger Car Unit Estimation for Heterogeneous Traffic Stream of Trunk Roads
    (Addis Ababa University, 2020-02) Ararsa, Bekele; Getu, Segni (PhD); Tamiru, Tilahun (Mr.) Co-advisor
    The study was conducted on capacity and passenger car unit estimation for heterogeneous traffic stream of trunk roads on Addis Ababa to Holeta, Addis Ababa to Sendafa, Addis Ababa to Sululta and Addis Ababa to Sebata road sections to estimate the PCU for different categories of vehicles, to analyze the variation of PCU values with respect to different interval of traffic volume, to compare and contrast the PCU resulted by Chandra’s and Homogenization coefficient methods and to estimate the road capacity. Different vehicle types occupy different spaces on the road, move at different speeds and start at different speeds. Especially in Ethiopia, this poses a problem when designing roads. A uniform measurement of vehicles is necessary to estimate the traffic volume and the capacity of roads with mixed traffic. This is difficult to achieve unless the different vehicle types are expressed in terms of a common standard vehicle unit. To attain these objectives on basic segment in flat terrain of selected study road sections, the data were collected by means of video recording by selecting favorable area on the study area. Depending on the concept of ERA manual, the vehicles are classified as standard car, 4WD, bus, truck and three wheeler. For each vehicle, data such as, vehicle class; number of vehicles and travel time were measured from vehicle travelled in study section between two thick white lines marked across the road width to provide reference line to arriving vehicles. The measured travel time was averaged for a fifteen minute time interval to determine the average mean speed. Density was computed from number of vehicle counted in given time interval and vehicle speed. The dimension of vehicles was obtained by physical measuring of the size of vehicles. From obtained data, traffic simulation were simulated by PTV VISSIM software and analyzed using SPSS and MS. Excel. The results indicate that, the PCU values for different types of vehicles were found to be different for different intervals of traffic volume. The result showed that value of PCU was decreasing as the volume of the road sections increase for all vehicles, except for three wheelers. The PCU resulted by Chandra’s method for 4WD, bus, truck and three wheeler are (1.43, 3.96, 4.63 and 0.64) were greater than the PCU value resulted by Homogenization coefficient methods (1.27, 2.7, 3.13, 0.85) respectively for all types of vehicles, except for three wheelers. The Capacity of the trunk road was obtained from the average PCU by using Green shield’s Model and Greenberg model for all road section depending on the direction of flow. The capacity resulted on each sections was lower than the value stated on the highway capacity manual 2010.